Integrated lead or so-called “wireless” suspensions and flexures for supporting read and/or write heads over the rotating recording media in magnetic disk drives are generally known and disclosed, for example, in the Bennin et al. U.S. Pat. Nos. 5,844,751 and 5,864,445. Suspensions and flexures of these types include conductive leads or traces which are formed integrally on the stainless steel or other spring material layer of the device. A layer of insulating material such as polyimide separates the conductive leads from the stainless steel layer. The integrated lead suspensions and flexures described in the Bennin et al. patents referred to above are manufactured from laminated sheets of material using “subtractive” processes. During these processes, portions of the individual layers of the laminated sheet which are to form the load beam, insulators, leads or other suspension and flexure features are protectively masked, and the sheet exposed to chemical, plasma, or other etchants to remove the undesired and unmasked portions. Another known approach for manufacturing integrated lead suspensions involves additive processes. During additive manufacturing methods the insulating and conductive lead layers are sequentially deposited onto or built up on the stainless steel base layer.
Preamplifier or other integrated circuit (IC) chips are sometimes mounted on integrated lead suspensions, typically either on the rigid region of the load beam or on a chip supporting extension off the side of the suspension mounting region. IC chips configured as conventional flip chips are often used in these applications due to their relatively low height profile (approximately 12 mils thick). However, the IC chip mounting regions on the suspensions often require formed offsets to provide sufficient clearance between even these relatively thin ICs and the spinning disk media or adjacent suspensions. As a result of their non-planarity, offset forms of these types can increase the difficulty of positioning and welding the flexures to the suspension load beams.
The ICs are mounted to the surfaces of the suspensions having the conductive leads by soldering the IC electrical terminals to bond pads in the conductive leads. Solder masks are typically formed over the conductive lead bond pads to prevent solder from spreading between and electrically shorting the leads during the mounting process. Patterned layers of photoimageable material (a coverlay) formed over the bond pads have been used as solder masks. However, this approach has presented a number of problems. The coverlay occasionally lifts away from the conductive leads during the soldering process (solder reflow), thereby allowing the solder to wick under the coverlay and short adjacent leads. During the developing process coverlay residue can form in the holes and prevent good electrical solder contact between the conductive lead bond pads and the IC chip terminals. Conductive adhesive is used to electrically interconnect one of the IC leads to the stainless steel suspension for grounding purposes, necessitating an additional process step and the use of adhesive dispensing equipment.
It is evident that there is a need for improved structures and methods for mounting IC chips to integrated lead suspensions. In particular, there is a need for structures and methods that minimize the height profile of integrated lead suspensions with ICs. Methods which can achieve these features without the need for additional processing steps or materials (e.g., conductive adhesive) beyond those used to manufacture the integrated lead suspension itself would be desirable. To be commercially viable, the structure and method must be capable of enabling the ICs to be efficiently mounted to the suspension with high-quality electrical connections.